cats, it is much less sensitive with as few as 36% of positive cases being identified. This has led to a new antigen test, the IDEXX SNAP® Feline Heartworm Antigen Test being developed and claims to have an increase of 15% in sensitivity over conventional antigen tests.
• Antibody Serology – This is the most sensitive blood test available for heartworm diagnosis in cats (Atkins, 1999). A positive result may indicate past or present exposure to infection and should be inter- preted in relation to clinical signs and other diagnostic tests.
Table 1. differentiating diagnostic features of Dirofilaria immitis and Dirofilaria repens microfilariae in the blood of dogs
Treatment of infections with adult worms requires surgical removal or treatment with an adulticide, the latter being contraindicated in cats. Steroids may be required for management of bronchitic signs in feline patients. Prophylaxis is desirable in travelling pets to reduce the risk of adult infection establishing.
Leishmania infantum
Leishmaniosis is caused by intracellular protozoan parasites of the genus Leishmania with Leishmania infantum being the predominant species in European cats and dogs. It has zoonotic potential and is a significant endemic zoonosis in southern Europe. Transmission occurs primarily through bites from infected phlebotomine sand flies, limiting the distribution of the parasite in Europe to the South of France and Southern Europe. Large numbers of cases however, are being seen outside of endemic areas in imported and travelled pets. Rapid diagnosis of infection is important as transmission can also occur through blood transfusion, vertical and venereal transmission. Identification of sub clinical carriers and rapid recognition of relevant clinical signs will allow prevention of these secondary modes of transmission as well as monitoring and treatment, where required, of infected pets.
Leishmaniosis caused by L.infantum is chronic in nature with a variety of presentations and periods of remission. Signs are due to immune complex deposition in various organs and include alopecia, hyperkeratosis, dermal ulcers, polyarthritis, ocular inclusion bodies, uveitis, hepatopathy, glomerulonephritis and neurological signs associated with spinal and CNS granulomas. Peri ocular alopecia (lunettes) are a classic sign and easily mistaken for atopy.
An Urban Experience
Leishmaniosis should always be considered as
a differential when presented with skin disease, lymphadenopathy or weight loss in dogs that has been present in endemic areas. A number of tests are available to aid in diagnosis.
• PCR – is very specific and highly sensitive when skin biopsies, lymph node or bone marrow aspirates are used but is much less sensitive when used on peripheral blood. PCR testing on conjunc- tival swabs has proved to be an effective non-invasive technique with sensitivity and specificity of 78.4 and 93.8% respectively (Geisweid et al, 2013).
• Serology – Seropositivity is found in 88-100% of dogs with clinical signs and can indicate a predisposition to developing clinical signs in subclinical dogs. Quantitative antibody testing on serum using IFAT (cut of 1/80 or 1/100) allows monitoring of possible clinical development in sub clinical cases, and monitoring of treatment in dogs that are in remission.
• Biopsies – of skin, lymph nodes or bone marrow. This is a highly sensitive and specific diagnostic method if multiple sites are taken but also more invasive than other tests.
Urinalysis is also a useful tool, revealing a proteinuria. The amount of protein in the urine is a more useful prognostic indicator than antibody titres.
Treatment carries a varying prognosis depending on progression of disease, hepatic and renal function. Infection is also life long and will require a life time of serological monitoring and possible treatment. Flare ups of disease are common and as a result, euthanasia should be considered as an option in clinically affected dogs if owners are unwilling or unable to undertake a lifetime of managemental care. The zoonotic aspects should also be discussed but kept in perspective, as there has never been a confirmed case of direct human infection from a dog or cat. Improvements in treatment success rates however, have made treatment a viable option, with the aim of treatment being remission
of clinical signs rather than clearance of infection. Infected cats and dogs should never be used for blood transfusions or breeding.
Treatment consists of allopurinol at 10-30mg/kg in combination with Meglumine antimonite (100mg/kg intravenous or subcutaneously) every 24 hours for 3-6 weeks or miltefosine orally (2mg/kg every 24 hours
for 4 weeks). The latter has the advantage in renal compromised patients of being metabolised solely by the liver. Gastrointestinal side effects however, from its use are common. Treatment with allopurinol alone may be required for up to 6 months after resolution of clinical signs to prevent relapse and some patients will need to remain on the drug indefinitely. Supportive treatment for hepatic and renal function may also be required.
Criteria
D.immitis
D.repens
Sheath
missing
missing
Approx. length (μm)
205-283
260-308
Width (μm)
5.0-6.5
6.0-8.0
Front end
conical
blunt
Posterior end
straight
hook shaped/bent
107